Aging Mechanism and Life Estimation of Photovoltaic Inverter DC-link Capacitors in Alternating Humid and Thermal Environment

DC-link capacitors play a vital role in managing ripple voltage and current in converters and various devices.This study focuses on exploring the aging characteristics of DC-link capacitors in alternating humid and thermal environments aligned with the operational conditions in photovoltaic and wind power applications.Adhering to relevant power equipment standards,we designed a 24-h alternating humid and thermal aging environment tailored to the requirements of DC-link capacitors.An aging test platform is established,and 20 widely used metallized polypropylene film capacitors are selected for evaluation.Parameters such as the capacitance,equivalent series resistance(ESR),and phase angle are assessed during aging,as well as the onset time and extent of aging at various intervals.This study focuses on the aging mechanisms,analyzing electrode corrosion,the self-healing process,and dielectric aging.Fitting the aging characteristics enabled us to calculate the lifespan of the capacitor and predict it under different degrees of capacitance decay.The results show that under alternating humid and thermal conditions,capacitance attenuation and ESR increase exhibit exponential nonlinearity,influenced by factors such as the oxidation and self-healing of capacitive metal electrodes,dielectric main-chain fracture,and crystal transformation.This study underscores the pivotal role of encapsulation in determining the aging decay time.

Emerging miniaturized energy storage devices for microsystem applications:from design to integration

The rapid progress of micro/nanoelectronic systems and miniaturized portable devices has tremendously increased the urgent demands for miniaturized and integrated power supplies.Miniaturized energy storage devices(MESDs),with their excellent properties and additional intelligent functions,are considered to be the preferable energy supplies for uninterrupted powering of microsystems.In this review,we aim to provide a comprehensive overview of the background,fundamentals,device configurations,manufacturing processes,and typical applications of MESDs,including their recent advances.Particular attention is paid to advanced device configurations,such as two-dimensional(2D)stacked,2D planar interdigital,2D arbitrary-shaped,three-dimensional planar,and wire-shaped structures,and their corresponding manufacturing strategies,such as printing,scribing,and masking techniques.Additionally,recent developments in MESDs,including microbatteries and microsupercapacitors,as well as microhybrid metal ion capacitors,are systematically summarized.A series of on-chip microsystems,created by integrating functional MESDs,are also highlighted.Finally,the remaining challenges and future research scope on MESDs are discussed.

Flexible lithium metal capacitors enabled by an in situ prepared gel polymer electrolyte

The rapid development of next-generation flexible electronics stimulates the growing demand for flexible and wearable power sources with high energy density.Li metal capacitor(LMC),combining with a Li metal anode and an activated carbon cathode,exhibits extremely high energy density and high power density due to the unique energy storage mechanism,thus showing great potential for powering wearable electronic devices.Herein,a flexible LMC based on an in situ prepared PETEA-based gel polymer electrolyte(GPE)was reported for the first time.Owing to the high ionic conductivity of PETEA-based GPE(5.75×10^(−3)S/cm at 20℃),the assembled flexible LMC delivers a high capacitance of 210 F/g at 0.1 A/g within the voltage range from 1.5 V to 4.3 V vs.Li/Li^(+),a high energy density of 474 Wh/kg at 0.1 A/g and a high power density of 29 kW/kg at 10 A/g.More importantly,PETEA-based GPE endows the LMC with excellent flexibility and safety,which could work normally under abuse tests,such as bending,nail penetration and cutting.The in situ prepared PETEA-based GPE simplifies the fabrication process,avoids the risk of leakage and inhibits the growth of Li dendrite,making LMC a promising flexible energy storage device for the flexible electronic field.

Reliability Analysis of Grid-Interfaced Filter Capacitors

Growing with the increased adoption of renewable energy for the power generation,the reliable and cost-effective operation of grid-connected inverters is of more and more importance.A filter is interfaced between an inverter and the utility grid to reduce the switching harmonics.According to the modulation scheme and the LCL filter impedance,the electrical stresses of the filter capacitor can be thoroughly investigated.With the help of the electro-thermal model,its long-term thermal stress can be obtained based on the mission profile like wind speed,ambient temperature.The reliability of the filter capacitor bank is obtained based on its individual capacitor reliability curves and reliability block diagram method.A case study on a 2MW wind turbine system demonstrates the relationship between the lifetime of the capacitor bank and the single capacitor.Moreover,the severe voltage and current stresses of the filter capacitors are analyzed during abnormal operations(e.g.,fault ride-through)with asymmetrical parasitic parameters.

TDDB improvement by optimized processes on metal-insulator-silicon capacitors with atomic layer deposition of Al_2O_3 and multi layers of TiN film structure

A metal-insulator-silicon （MIS） capacitor with hemi-spherical grained poly atomic layer deposition （ALD） deposited Al2O3 and multi-layered chemical vapor deposition （CVD） TiN structure is fabricated. The impact of the deposition process and post treatment condition on the MIS capacitor＇s time-dependent dielectric breakdown （TDDB） performance is also studied. With an optimized process, it is confirmed by Auger electron spectroscopy and secondary ion mass spectrometry analysis that the Al（CH3）3/O3-based ALD Al2O3 dielectric film is carbon free and the hydrogen content is as low as 9 × 1019 cm-3. The top electrode TiN is obtained by multi-layered TiCl4/NH3 CVD deposited TiN followed by 120 s post NH3 treatment after each layer. This has higher diffusion barrier in preventing impurity diffusion through TiN into the Al2O3 dielectric due to its smaller grain size. As shown in energy dispersive X-ray analysis, there is no chlorine residue in the MIS capacitor structure. The leakage current of the capacitor is lower than 1 × 10-12 A/cm2. No early failures under stress conditions are found in its TDDB test. The novel MIS capacitor is proven to have excellent reliability for advanced DRAM technology.